(1) Field of Invention
This invention relates to liquid, aqueous, stable, effective, safe, non-scratching hard surface cleaning compositions which have shear thickening properties and are commonly referred to as scouring cleansers. The compositions are physically stable, do not separate, whereby the user is assured of the optimum performance to be expected from the various components and their amounts and ratios with respect to one another. These compositions are also safe and do not scratch the usual surfaces to be cleaned, such as glass, porcelain, ceramic, plastic, metal, wood, painted wood (enameled and lacquered). The compositions of the instant invention because of their dilatant properties are especially useful in the cleaning of vertical surfaces.
(2) Prior Art Discussion
The art is replete with liquid scouring compositions alleged to perform in a safe and effective manner, while others are stated to be physically and chemically stable.
Some examples of prior art scouring compositions include U.S. Pat. No. 4,005,027 which describes compositions which include clay and insoluble abrasive. Only inorganic abrasives are shown and nonionics are not used. The compositions include surfactants which are bleach stable. It is alleged that the products are physically stable and also do not "appreciably run along vertical surfaces" (column 10, lines 45-47). Such stability is a manifestation of a false body fluid formed when using the smectite and attapulgite clays necessary in such compositions. The compositions of U.S. Pat. No. 4,116,849 are very similar to those in U.S. Pat. No. 4,005,027. In addition, U.S. Pat. No. 4,116,849 discloses thickening agents instead of the preferred smectite and attapulgite clays, such as collodial silica, polystyrenes, sulfonated polystyrenes, polyethylene, oxidized polyethylenes, polypropylene, copolymers of styrene with methacrylic acid, methyl or ethyl acrylate, vinyl acetate, among others; patentee states that " . . . ethoxylated nonionic surfactants are to be avoided." Neither of these two patents disclose soaps or fatty acids as suitable materials as well. U.S. Pat. No. 4,240,919 describes compositions of multivalent stearate soap, water and water-insoluble abrasive. Various abrasives are disclosed and among the "organic" types are "melamine, urea formaldehyde resins, ground rigid polymeric materials, such as polyeurethane foam . . . " (column 3, lines 10-12). Optionally, there may be present "substantially any surfactant materials which are compatible with the other components in the composition of the present invention . . . ". These include watersoluble anionic, nonionic, amphoteric, cationic and zwitterionic surfactants." (column 3, lines 57-62). Further reference is made to U.S. Pat. Nos. 4,051,056 (expanded perlite as abrasive), 4,457,856 (polyacrylate abrasive), German 1,956,616 (polyvinyl chloride as abrasive) and 3,645,904 (skin cleanser containing polymer abrasive material).
All of the compositions disclosed in the aforementioned prior art do not possess shear thickening properties. These compositions of the prior art are shear thinning at 25.degree. C. as the rate of shear is increased. In other words, as the shear rate is increased as in the process of scrubbing, the viscosity of the composition will decrease. The compositions of the instant invention exhibit shear thickening properties at 25.degree. C. which means that as the shear rate is increased the compositions will shear thicken. In a scrubbing process which causes an increase in the shear rate, the viscosity of the composition will increase and the composition will exhibit gel-like properties. This shear thickening of the compositions of the instant invention make them especially useful on vertical surface because of their tendency not to run off of the vertical surface which is being cleaned as compared to the prior art compositions.
U.S. Pat. No. 4,575,530 (Mar. 11, 1986) describes hydrocarbon solution additives which are polyampholytes which incorporates cationic and anionic moieties on the same polymeric backbone. These hydrocarbon solutions have shear thickening properties.
U.S. Pat. No. 4,536,539 (Aug. 20, 1985) claims include increasing the viscosity of water under increasing shear rates (22.0--approaching 100 sec.sup.-1). This shear thickening behavior is primarily attributed to the increase in apparent molecular weight of the interpolymer complex through formation of intermolecular ionic linkages.
The instant invention teaches that these thickened silicates show shear thickening (dilatency) which means that the viscosity increases as shear rate at 25.degree. C. is increased. Furthermore, the viscosity values at each shear rate are independent of the timescale of the experiment. Once the shear rate is applied, the viscosity reaches a steady value after a few seconds up to several minutes. Shear thickening occurs when the applied shear forces predominate the interparticle forces. The shear forces change the dispersion from a certain degree of order to clusters of particles. Shear thickening behavior is dependent on particle shape, size and size distribution; particle volume fraction type and strength of inter-particle interaction; continuous phase viscosity; and the experimental parameters characterizing the shear thickening. These parameters include the type, rate, and duration of the applied shear deformation.